In many applications, it can be difficult to directly connect a die to another circuit or substrate, such as a printed circuit board (PCB). For example, if an integrated circuit (IC) is to be mounted on a PCB, wiring of the PCB may be too coarse to connect fine contacts of the integrated circuit. In such applications, the die and PCB may be interconnected through an interposer. An interposer is a silicon body having a first set of fine contacts (e.g., micro-bumps) on one side, to which a die may be bonded, and a second set of coarse contacts (e.g., C4 solder balls) on the other side for bonding to another chip, substrate, PCB, etc. Wiring and vias of the interposer may connect fine-pitched die contacts located on one side of the interposer to a coarser contact array on the opposite side of the interposer.
The set of fine or course contacts that bonds two ICs (e.g., an IC and an interposer) includes an array of bumps (e.g., micro-bumps or C4 solder balls) on the backside of one IC and a matching array of pads on the front-side of the second IC. For ease of reference, a micro-bump and pad pair may be collectively referred to herein as a micro-bump contact.
Defects may occur in new fabrication processes. To improve manufacturing processes, manufactured ICs are tested to detect undesirable defects, such as open and short circuits in micro-bump contacts. Once detected, these defects are analyzed to determine the location and type of the defects so the manufacturing processes may be modified to eliminate the resulting defects. However, the testing of micro-bump contacts can be difficult. Due to the large number of micro-bump contacts, it may take several hours to scan each micro-bump contact to determine the location of a failure. Determination of the location of the defect can be critical to the improvement of the fabrication processes.